The present invention broadly relates to the art of positive-displacement pumps, and in particular concerns a new and improved construction of electromagnetically-actuatable rotary vane-type pump incorporating radially displaceable sliding vanes or plates and wherein such pump can be employed as a hydraulic brake.
There are known to the art numerous types of electromagnetically-actuatable brakes, such as for instance, eddy current brakes wherein the braking effect is reduced with decreasing rotational speed and which cannot be used however as a standstill brake. Moreover, the removal of the heat which evolves during the braking action is associated with certain difficulties.
Another state-of-the-art magnetic brake uses a filling of magnetizable granules or filings which are admixed with a braking oil and when the excitation current is turned-on form more or less solid bridges between the stator and the rotor. What is disadvantageous with this type of brake is that certain frictional losses also prevail during idling.
Finally, different constructional manifestations of brakes are known to the art which work according to the principle of a positive-displacement pump and circulate a braking fluid, the braking action being produced by a throttle location which is arranged between the pressure side and the suction side of the pump. Such positive-displacement pumps are typically reciprocating or piston pumps embodying a multiplicity of radial pistons arranged about an eccentric by means of which these pistons are actuated. Also in this case during idling there cannot be avoided an appreciable braking action. Moreover, such type brake requires a considerable amount of space.